[rs.pect]

Then save players in a race to PVar.

pawn Код:

//When player joins race
SetPVarInt(playerid, "InRace", 1);

//When player leaves race
SetPVarInt(playerid, "InRace", 0);

//In-race players loop
for(new i, mp = GetMaxPlayers(); i < mp; i++)
{
    if(IsPlayerConnected(i) && GetPVarInt(i, "InRace") == 1)
    {
        //some code
    }
}